Photographic emulsions, oil in water emulsion, or gelatin solutions in a sol state prepared have hitherto been stored in vessels such as a stainless pot which are placed in a refrigerator in which the emulsions or solutions in a sol state are cooled through thermal conduction from the outside of a vessel to transform into a gel state for storage. In this method the emulsions or solutions in a sol state are compelled to be slowly cooled after being placed in the refrigerator and, as a result, subjected to relatively high temperatures for a long period of time, which is not favorable for photographic properties. For example, in X-ray photographic emulsions in which grains with relatively greater diameters are employed, the grains are precipitated before setting, causing fluctuations in silver distribution. Further, in an oil in water emulsion containing a volatile solvent, the volatile solvent is vaporized and condensed again in a pot which is placed in a refrigerator for storage, developing trouble due to droplets of the solvent.
To solve these problems, a method has been disclosed in JP-B-52-14717 (The term "JP-B" as used herein means an "examined Japanese patent publication"). That is, in a structure having a number of thin wall pipes provided at appropriate intervals in which cold or warmed water is allowed to flow through the outside of the pipes, a photographic emulsion is placed in the thin wall pipes and cooled by circulation of cold water to be transformed into a gel state. In order to take out the gel thus prepared, only the exterior of the gel is then melt again by circulation of warmed water (means 1).
Further, a process of rapid gelation that a sol-form substance is sprinkled in an evacuated vessel to be cooled by absorption of heat of vaporization has been described in U.S. Pat. No. 3,847,616 and U.S. Pat. No. 3,910,812 that are both corresponding to JP-B-50-31447, JP-A-60-104937 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-B-3-5210, and JP-B-3-68735 (means 2).
The above-mentioned means 1 requires repeating cooling and melting alternately using one vessel, resulting in a hideous waste of time and energy. In means 2, it is difficult to maintain the amount of water contained in an emulsion at a constant value, when the gel prepared is taken out of the vessel for storage. Hence, water must be added to adjust the amount of silver after melting the gel again.